title: Hydrogen generation by water reduction with [Cp*(2) Ti(OTf)]: identifying elemental mechanistic steps by combined in situ FTIR and in situ EPR spectroscopy supported by DFT calculations.
abstract: A detailed mechanism of hydrogen production by reduction of water with decamethyltitanocene triflate [Cp*2 Ti(III) (OTf)] has been derived for the first time, based on a comprehensive in situ spectroscopic study including EPR and ATR-FTIR spectroscopy supported by DFT calculations. It is demonstrated that two H2 O molecules coordinate to [Cp*2 Ti(III) (OTf)] subsequently forming [Cp2 *Ti(III) (H2 O)(OTf)] and [Cp*Ti(III) (H2 O)2 (OTf)]. Triflate stabilizes the water ligands by hydrogen bonding. Liberation of hydrogen proceeds only from the diaqua complex [Cp*Ti(III) (H2 O)2 (OTf)] and involves, most probably, abstraction and recombination of two H atoms from two molecules of [Cp*Ti(III) (H2 O)2 (OTf)] in close vicinity, which is driven by the formation of a strong covalent TiOH bond in the resulting final product [Cp*2 Ti(IV) (OTf)(OH)].
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert Einstein-Straße 29 A, 18059 Rostock, Fax: (+49) 381-1281-51244. dirk.hollmann@catalysis.de.
authors.forename: Dirk
authors.initials: D
authors.lastname: Hollmann
authors.forename: Kathleen
authors.initials: K
authors.lastname: Grabow
authors.forename: Haijun
authors.initials: H
authors.lastname: Jiao
authors.forename: Monty
authors.initials: M
authors.lastname: Kessler
authors.forename: Anke
authors.initials: A
authors.lastname: Spannenberg
authors.forename: Torsten
authors.initials: T
authors.lastname: Beweries
authors.forename: Ursula
authors.initials: U
authors.lastname: Bentrup
authors.forename: Angelika
authors.initials: A
authors.lastname: Brückner
keywords: EPR spectroscopy; IR spectroscopy; density functional calculations; hydrogen production; titanium; water activation